Landing zone designation system and method

ABSTRACT

A landing zone designation system is provided that includes a master and a slave landing strobes. A detector on an aircraft can detect master and slave optical signals, and a processor can be coupled to the detector to compute placement of the aircraft relative to the master and slave landing strobes. A method is provided for designating a landing zone for an aircraft. The method includes emitting first and second optical signals, where a determination is made whether the aircraft is to land at a first landing zone or a second landing zone depending on a difference between the first optical signal and the second optical signal. A distance to landing within the determined first landing zone or the second landing zone can also be determined.

BACKGROUND

A landing craft may need to land at a site for a pick up or drop offoperation. The site can be on ground or on water, and is henceforthreferred to as a landing zone. The landing craft, or aircraft, isgenerally above the landing zone in need of identifying a proper sitefor landing during pick up or drop off.

The aircraft includes personnel or guidance equipment used to detect andland at or near the landing zone. The aircraft includes either afixed-wing or rotary-wing aircraft. If the landing zone is visuallydegraded, possibly due to cloud cover, fog, or dust and sediment stirredby the aircraft, it may be difficult for the equipment or personnelwithin the overhead aircraft to visually detect the landing zone. Thelanding zone may therefore include one or more beacons, or strobes,placed at or near the landing zone. The landing strobe or strobes can beconfigured to emit visible or invisible light that is detectable by theoverhead aircraft, henceforth referred to as an aircraft albeitunderstood to encompass a watercraft provided there is proper landinggear underwater or floatation upon the water. A landing strobe placed ator near the landing zone can therefore help guide the aircraft toward,for example, a friendly landing zone.

SUMMARY

In accordance with at least one example of the disclosure, a landingzone designation system comprises a master landing strobe configured toemit a master optical signal at periodic intervals. A slave landingstrobe spaced a predetermined distance from the master landing strobecan be configured to receive the master optical signal and to generate,from the master optical signal, a slave optical signal synchronized tothe periodic intervals. The slave landing strobe can be spaced apredetermined distance from the master landing strobe and can beconfigured to receive the master optical signal and to generate, fromthe master optical signal, a slave optical signal synchronized to theperiodic intervals. A detector can be provided on an aircraft fordetecting the master and slave optical signals. A processor can becoupled to the detector to compute placement of the aircraft relative tothe master and slave landing strobes.

In accordance with at least one other example of the disclosure, alanding zone designation system comprises a first landing zone thatincludes a first plurality of landing strobes arranged in a first spacedgeometric shape and configured to emit a first optical signal. A secondlanding zone can include a second plurality of landing strobes arrangedin a second spaced geometric shape and configured to emit a secondoptical signal. A detector can be provided on an aircraft spaced fromthe first landing zone and the second landing zone, wherein the detectoris configured to detect the first optical signal and the second opticalsignal. A processor can be coupled to the detector for determiningwhether the aircraft is to land at the first landing zone or the secondlanding zone depending on a difference between the first optical signaland the second optical signal.

In accordance with another example of the disclosure, a method isprovided for designating a landing zone for an aircraft. The methodincludes emitting a first optical signal synchronized to a first masterlanding strobe at a first landing zone. A second optical signal can besynchronized to a second master landing strobe at a second landing zone.The first optical signal and the second optical signal can be receivedby the aircraft. A determination can be made whether the aircraft is toland at the first landing zone or the second landing zone depending on adifference between the first optical signal and the second opticalsignal. A distance to landing within the determined first landing zoneor the second landing zone can then be determined.

A method can also be provided for determining a distance to landing foran aircraft, by first storing a pixel number rate of change betweenlanding strobes corresponding to different heights of the aircraft abovea landing zone. The approach can then begin by the aircraft approachingtoward the landing zone. Computing a rate of pixel change can thenoccur, and determining the distance to landing at a height above thelanding zone corresponding to the rate of change at that height.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various examples, reference will now bemade to the accompanying drawings in which:

FIG. 1 shows a side partial cross-sectional and plan view of a landingstrobe configured with moveable vanes in accordance with variousexamples;

FIG. 2 shows a top view of the vanes extending outward from the landingstrobe in accordance with various examples;

FIG. 3 shows a side partial cross-sectional and plan view of the landingstrobe configured with vanes that are mechanically moveable inaccordance with various examples;

FIG. 4 shows a side partial cross-sectional and plan view of the landingstrobe configured with vanes that are electrically moveable inaccordance with various examples;

FIG. 5 shows a block diagram of a system for moving the vane or vanes inaccordance with various examples;

FIG. 6 shows a side view of the landing strobe deployed at a landingzone in accordance with various examples;

FIG. 7 shows a block diagram of a system for assigning (preferablythrough user-actuated switches) an optical signature strobe output toone or more landing strobes, and for assigning an optical radiationpattern from the landing strobes in accordance with various examples;

FIG. 8 shows a schematic diagram of a system for assigning a uniquesignature strobe output and radiation pattern from one or more landingstrobes surrounding a landing zone in accordance with various examples;

FIG. 9 shows a schematic diagram of a system for determining distance tolanding at a descent distance depending on pixel separation between apair of strobes shown at a landing zone in accordance with variousexamples;

FIG. 10 shows a top view of strobes surrounding a landing zone detectedby a camera in different frames as the aircraft is approaching thelanding zone for determining pixel separation in accordance with variousexamples;

FIG. 11 shows a block diagram of a system for detecting optical signalsfrom one or more landing strobes in one or more landing zones inaccordance with various examples;

FIG. 12 shows a flow diagram of a method for designating landing of anaircraft in a landing zone in accordance with various examples;

FIG. 13 shows a flow diagram of a method for deploying one or morelanding strobes in one or more landing zones in accordance with variousexamples;

FIG. 14 shows a flow diagram of a method for determining pixel distancebetween strobes of a camera frame at a descent distance above a landingzone for computing distance to landing at the descent distance inaccordance with various examples;

FIG. 15 shows a graph of rate of pixel change relative to height above alanding zone in accordance with various examples; and

FIG. 16 shows a flow diagram of a method for computing a distance tolanding based on a stored rate of pixel change relative to height abovethe landing zone in accordance with various examples.

DETAILED DESCRIPTION

This description is generally directed to vision enhancement throughturbid media, such as fog, cloud cover, dust or sediment that occupy anoverhead vehicle, or operator of that vehicle, field of view. Theoverhead vehicle comprises any vehicle that can land on ground or water.Ground can be the floor of a body of water. Henceforth, the overheadvehicle is referred alternatively as an aircraft, even though the term“aircraft” hereinafter interchangeably refers to watercraft. Thedisclosed description includes devices, systems, and methods to enhancethe ability to perceive light emission from sources upon or within alanding strobe. The light sources include an optical emitter that canemit light either in the visible or invisible wavelength ranges. Theoptical signal emitted from the optical emitter can be in the infraredwavelength range, such as short wave infrared (SWIR), medium waveinfrared (MWIR), or long wave infrared (LWIR). The optical emitter caninclude xenon, halogen, flash, incandescent, light emitting diode (LED),or any other visible or invisible optical signal source. The opticalemitter can include a filter or lens to select the upward radiationpattern, or can direct the radiation in an omni-directional pattern.

This description is also directed to a light detection system, and amethod for detecting the optical signals emitted from the opticalemitters upon or within one or more landing strobes. The detector systemcan be employed on the overhead aircraft to detect that which isundetectable by the human eye, and accordingly, can include an enhancedcontrast-based, image processing system using, for example, forwardlooking infrared (FLIR) technology. In one example, the detector systemcan include a pixelated sensor, an optical bandpass filter or set offilters, an imaging lens, and a processor. The detector system canfurther include a memory coupled to the processor to store the pixelateddata as well as other information corresponding to the optical signal orsignals sent from the landing strobe or strobes. The detectors systemcan be mounted on or within the aircraft, on a standalone device withinthe aircraft, or on the goggles or headpiece of one or more personnelwithin the aircraft.

Referring to the drawings, FIG. 1 shows a landing strobe 100, accordingto one example. Landing strobe 100 can be deployed from an overheadaircraft or by personnel on the ground. Whether deployed from a spaceddistance above the ground, such as from an aircraft, or deployed on theground, once landing strobe 100 is deployed, a central axis 102 isconfigured to extend substantially vertical (i.e., substantiallyperpendicular to a surface of ground 104).

Central axis 102 extends preferably through the center of landing strobe100. Included with landing strobe 100 is an optical emitter 106. Opticalemitter 106 can emit a radiation pattern 108 that extends at adjustableradial angles and distances from central axis 102. The radiation pattern108 from optical emitter 106 can comprise coherent or non-coherentlight, with the outer extents of pattern 108 adjustable by angle Φaround central axis 102.

Landing strobe 100 further includes at least one vane 110 (dependingupon the number of vanes, 110 a, 110 b, etc.) extending radially outwardand at angle from central axis 102. Each vane 110 has a distal end 112(depending on the number of vanes, 112 a, 112 b, etc.) that extendsfurthest from the landing strobe 100. Each vane 110 also has a proximalend 114 (114 a, 114 b, etc.) that can be inside of the outer housing oflanding strobe 100.

Each vane includes a blade that has a relatively flat surface whichextends from the proximal end 114 to the distal end 112. Each blade canrotate around the central axis 102 during descent from an overheadaircraft to ground 104, or each blade can pivot around pins 116 (116 a,116 b, etc.) arranged near the proximal end 114 and preferably withinthe housing of landing strobe 100. If, for example, landing strobe 100is dropped from an overhead aircraft, the force F of air upon theelongated blade of each vane 110 will push each vane 110 to a firstposition shown in phantom line. The amount of force F caused by the airresistance upon each vane 110 during descent of landing strobe 100 willovercome a biasing force of a biasing mechanism 120 (120 a, 120 b, etc.)applied to the proximal end 114. Biasing mechanism 120 is any mechanismthat would draw the corresponding distal end 112 toward ground 104.However, if the air resistance force F exceeds the downward force ofbiasing mechanism 120, then the vanes 110 will be configured with distalends 112 facing upward and away from ground 104. For example, thebiasing mechanism 120 can be a spring. As shown in FIG. 1, biasingmechanism 120 b is shown with the spring expanded when the correspondingvane 110 b is facing upward. However, the spring of biasing mechanism120 a is shown compressed after descent is completed and there is nolonger upward air resistance force F, thereby compressing the spring ofbiasing member 120 a.

Regardless of the configuration of the biasing member 120, whether aspring or not, biasing mechanism 120 is preferably configured insidelanding strobe 100 to draw the corresponding vane 110 downward againstthe upward air resistance force F. When descent has ended and airresistance no longer is applied, the biasing mechanism 120 will forcethe vanes 110 and corresponding distal ends 112 to a second positionagainst the surface of land 104.

Landing strobe 100 still further includes a weighted base 122 centeredradially about the central axis 102, below a center of gravity 124 andalso below the pivot pins 116. The amount of weight within the weightedbase 122 can vary depending on the overall weight of landing strobe 100,provided the amount of weight is sufficient to maintain the center ofgravity 124 below the pivot pins 116, and to also maintain the centralaxis 102 in a vertical position substantially collinear with a descentvector and substantially perpendicular to the underlying surface ofground 104. Included within landing strobe 100 is a switch preferablymounted on the housing of landing strobe 100 that, when actuated, turnson emitter 106. The switch can be actuated either manually by a userbefore launching strobe 100, or by a user on the ground after the strobeis launched. The switch can also be activated remotely by aircraftpersonnel or remotely by a user on the ground after the landing strobe100 is launched. It may be desirable to activate the optical emitter 106after the landing strobe 100 is placed on the ground so as to disguiseillumination from unauthorized personnel during descent. A battery 128can also be included within landing strobe 100 to supply power to thecomponents within landing strobe 100, including optical emitter 106.Battery 128 includes any device that can store electrical energy and canbe charged or recharged either prior to deployment or after deploymentwhen the landing strobe 100 is on ground 104.

FIG. 2 shows a top view of landing strobe 100 according to anotherexample. Landing strobe 100 includes optical emitter 106, and at leastthree but preferably four vanes 110 (e.g., 110 a, 110 b, 110 c, and 110d). The proximal end 114 of each vane 110, shown as 114 a, 114 b, 114 c,and 114 d, are inside the outer housing of landing strobe 100, pivotalabout the corresponding pins 116 (e.g., 116 a, 116 b, 116 c, and 116 d).The distal ends 112 (e.g., 112 a, 112 b, 112 c, and 112 d) can include aspaced set of protrusions 114 (e.g., 114 a, 114 b, 114 c, and 114 d)that can extend outward and possibly downward into a point or apex. Whendescent has ended and the distal ends 112 extend downward, the series ofprotrusions 114, and specifically the tips of each protrusion 114 pierceinto the ground 104 (FIG. 1) caused by the downward force of the biasingmechanism 120 (FIG. 1). The combination of the protrusions 114 and thedownward biasing force of biasing mechanism 120, frictionally engage theground 104 to keep the landing strobe 100 in the proper position withcentral axis 102 substantially perpendicular to the upper surface ofground 104.

FIG. 3 illustrates landing strobe 100 according to another example.Specifically, in addition to the biasing member 120 of FIG. 1, or inlieu of the biasing member 120, landing strobe 100 can include anactuator 300 corresponding to each vane (e.g., 300 a and 300 b) andcoupled to the proximal ends of respective vanes 110 (e.g., 110 a and110 b). Actuator 300 operates similar to the biasing mechanism 120 as acomponent of landing strobe 100 responsible for moving the correspondingvane 100. Actuator 300 can be a component coupled to receive anactuation signal. In the example of FIG. 3, the actuation signal can bea mechanical signal of, for example, mechanical force 302 applied to anarm 304 that releases a latch within each actuator 300 (e.g., actuator300 a and 300 b). Release of the latch will cause movement of each vane110 from an upward angle first position to a downward angle secondposition when the actuation signal 302 impact force 306 is applied totransducer 310. Accordingly, transducer 310 is a mechanical transducerthat sends an actuation signal 302 to corresponding actuators 300 tomove corresponding vanes 110 to a downward second position, where thedistal ends of each vane can contact the ground.

FIG. 4 illustrates landing strobe 100 according to yet another example.Landing strobe 100 of FIG. 4 can include an electrical transducer 410that, upon receiving impact force 406, transducer 410 sends an actuationsignal 402 across, for example, a wire to actuators 400 (e.g., 400 a and400 b). Upon receiving the actuation signal 402 when landing strobe 100impacts ground, actuator 400 moves the corresponding vane 110 (e.g., 110a and 110 b) downward so that the distal ends of each vane 110 contactground. The actuators 300 (FIG. 3) and 400 (FIG. 4) serve to level thestrobe 100 so that the central axis 102 points upward in a substantiallyvertical direction. The directionality is described in reference to FIG.6. Regardless of whether the vanes are moveable by a biasing mechanismor an electrical or mechanical transducer coupled to an electrical ormechanical actuator, each landing strobe 100 includes a weight 122 nearits base, and a optical emitter 106 mounted substantially opposite ofthe base. The optical emitter 106 can include one or more emitterspossibly arranged in an array.

FIG. 5 shows a block diagram of a landing strobe system 500 for movingthe vanes 110 (FIGS. 1-4) in accordance with various examples. Whenreceiving an input, such as upward force on the landing strobe 100during impact, a mechanical or electrical transducer 310/410 can send anactuation signal to the corresponding mechanical or electrical actuator300/400 (FIGS. 3 and 4). However, if the actuator is a biasing mechanism120 (FIG. 1), then the biasing mechanism 120 will move the correspondingvane 110 downward rather than the mechanical or electrical actuator300/400. Depending upon which mode of operation is used, the transducer310/410 as well as actuator 300/400 can be eliminated in favor of simplya biasing mechanism 120. Alternatively, the biasing mechanism 120 can beeliminated in favor of a transducer 310/410 and an actuator 300/400.Additionally, the actuator 300/400 can operate similar to biasing member120, or actuator 300/400 can also include a separate biasing member 120to maintain the electrically or mechanically actuated vanes 110 in theirdownward biased positions after having been actuated. The actuator300/400, whether operating separate from or as part of biasing mechanism120, can actuate the optical emitter 106 when the landing strobe 100impacts ground. Therefore, instead of the switch 126 (FIG. 1) activatingthe optical emitter 106 either locally or distally from landing strobe110, the actuator 300/400 can automatically turn on or actuate theoptical emitter 106 during impact.

FIG. 6 shows a side view of landing strobe 100 after decent has ended,or after landing strobe 100 is placed by personnel on ground 104. Atleast three vanes 110 (e.g., 110 a, 110 b, and 110 c) are shown moved toa second position upon impact or by personnel on ground 104. Either thebiasing mechanism 120 and/or the actuator 300/400 (FIG. 5) moves thevanes 110 to the second position, but at dissimilar angles Φ₁ and Φ₂.Thus, the downward force 600 a may be the same as or greater than thedownward force 600 b, causing the difference in angular orientation ofcorresponding vane 100 a and 110 c. The difference in angularorientation and specifically the downward angle orientation of each vaneis biased downward by different forces on corresponding vanes to ensurethat the central axis 102 remains substantially vertical and alsosubstantially perpendicular to ground 104, even though the upper surfaceof ground 104 can have an uneven topology.

The vertical orientation of central axis 102 is beneficial if theradiation pattern 108 of optical emitter 106 is to extend in a conicalfashion substantially upward. Arranging the radiation pattern 108substantially upward, after impact or when the ground personnelactivates the optical emitter 106, minimizes unwanted personnel orinstrumentation at or near ground level from optically detecting theupwardly directed optical signal. It is desirable that only friendlypersonnel be allowed to see the landing strobe output, those personnelbeing above the landing strobe, possibly within an aircraft and possiblyhaving appropriately tuned optical detection systems.

FIG. 7 shows a block diagram and partial cross-sectional view of asystem for assigning an optical signature strobe output to one or morelanding strobes. The signature strobe output preferably different foreach landing strobe 100 so that each landing strobe 100 has an opticalsignal output from its optical emitter 106 that is unique to thatlanding strobe. There may be applications, however, when a group oflanding strobes 100 corresponding to a single landing zone may each havethe same signature strobe output. Therefore, the optical signal of eachlanding strobe 100 of a corresponding landing zone will have the sameoptical signal output to uniquely identify that landing zone frompossibly other landing zones nearby.

FIG. 7 illustrates a system 700 for assigning a signature strobe outputfrom a landing strobe 100 unique to that landing strobe, or assigning asignature strobe output unique to a group of landing strobes 100 withinor near a landing zone unique to that landing zone. The signature strobeoutput is assigned as a frequency or a frequency range unique to thelanding strobe 100 or group of landing strobes 100, a wavelength orrange of wavelengths unique to landing strobe 100 or group of landingstrobes 100, or a repetitive and periodic series of pulses unique tolanding strobe 100 or a group of landing strobes 100. For example, as alanding strobe 100 produces a series of optical signals at periodicintervals, each optical signal can be set to a unique optical signalfrequency, a unique optical signal wavelength, and/or a unique series ofcoded pulses. The unique frequency and/or wavelength is set via afrequency/wavelength selector 702. The unique repetitive and periodicseries of coded pulses are set by a pulse code selector 704. Forexample, a landing strobe 100 or group of landing strobes 100 associatedwith a landing zone can be set to output an optical signal of asignature strobe output to a repetitive and periodic series of codedpulses that are two long pulses, followed by a short pulse, followed byone long pulse unique to that landing strobe 100 or group of landingstrobes 100, rather than a repetitive and periodic series of four shortpulses followed by a long pulse. The signature strobe output set withinthe frequency/wavelength selector 702 and/or the pulse code selector 704occurs via a user input. Selectors 702 and 704 can thereby be consideredas an input device selector having a port configured to receive an input(INPUT) for setting the signature strobe output. The port can either bea wired port, such as a switch that is configured on and coupled to thelanding strobe 100, and is user-actuated and configured to receive theinput from a user. The port can be wired and can receive the input froma device held by a user and physically coupled to the wired port. It ispreferred that the port is a wired port, and more specifically a switchthat is actuated by a user to select the signature strobe to be outputfrom the landing strobe or strobes 100. Alternatively, however, the portcan be a wireless port configured to receive the input from a device inremote wireless communication with the wireless port, provided thewireless link or channel does not transmit in interference with otheraircraft communication systems, such as navigation and communication toand from base. The device can be any device in which a user can accessthe wired or wireless port. The device, if accessing the portwirelessly, can be in an aircraft 706 spaced from the input port andspecifically, the input devices or selector 702 and 704.

The input devices or selectors 702 and 704 receive an input via thecorresponding port and configure, or set, the optical emitter 106 outputto the appropriate frequency, frequency range, wavelength, wavelengthrange, and/or pulse code. The signature strobe output can be set orconfigured within a storage device communicatively coupled to opticalemitter 106. If the signature strobe output is a frequency, frequencyrange, wavelength, wavelength range, then the signature strobe outputcan be set within a modifiable optical filter communicatively coupled tolens 708.

Once configured or set within the input device of selectors 702 and 704so that the appropriate and unique signature strobe output is emittedfrom the optical emitter 106 as an optical signal having a radiationpattern 108, aircraft 706 is configured to detect the signature strobeoutput that is unique to landing strobe 100 or group of landing strobes100 of a landing zone. Aircraft 706 therefore includes a detector 710that can detect the signature strobe output unique to a landing strobe100 or a group of landing strobes 100, and therefore discern one landingstrobe 100 from another and/or one landing zone from another landingzone.

FIG. 7 further illustrates system 700 for adjusting the radiationpattern 108 at different angles relative to central axis 102. Theadjustable radiation pattern 108 can be modified by moving, for example,a reflective cylindrical housing 712 at different distances 714 aboveoptical emitter 106 and/or lens 708. The further the cylindrical housing712 extends above the optical emitter 106, the lessened amount ofradiation pattern 108 extends at an angle relative to central axis 102.If housing 712 is moved downward so that the upper extents of housing712 are drawn toward optical emitter 106, the greater the outer extentof radiation pattern 108, and the greater is the outer extents angle ofthe optical signal relative to central axis 102. Lens 106 is preferablyfixed within the cylinder of housing 712, with the upper extents ofhousing 712 moveable relative to the lens 106, or vice versa. Thus, theoptical signal 720 and, if uniquely set, signature strobe output 722 canbe configured in various ways to radiate upward toward aircraft 706 and,specifically, detector 710 at different radiation patterns and,specifically different radiation patterns having different outer extentsor angles relative to central axis 102.

FIG. 8 shows a schematic diagram of a system 800 for assigning a uniqueoptical signature and pattern from one or more landing strobes 100(e.g., 100 a, 100 b, 100 c and 100 d) of two or more landing zones LZs810 (e.g., LZ1 810 a and LZ2 810 b). For example, the landing zone 810 aas well as landing zone 810 b each emits an optical signal 720 fromcorresponding landing strobes 100 a-c and 100 d-f to detector 710 ofaircraft 706. However, landing strobes 100 a-c can be configured with asignature strobe output 722 a that is different from the signaturestrobe outputs 722 b from landing strobes 100 d-f of landing zone 810 b.Due to that difference, where signature strobe output 722 a is unique toLZ1 810 a, and signature strobe output 722 b is unique to LZ2 810 b,personnel within aircraft 706 can utilize detector 710 to determinewhich landing zone (LZ1 versus LZ2) aircraft 706 is to land. Forexample, the frequency or wavelength 802 a-c of the optical signal 720of LZ1 810 a can be the same (unique to LZ1 810 a) but different fromthe frequency or wavelength 802 d-f of the optical signal 720 from LZ2810 b. Thus, the frequency/wavelength of the optical signal of signaturestrobe 722 a can be different from that of signature strobe 722 b which,when detected by detector 710, allows the landing zone designationsystem 800 to determine which landing zone aircraft 706 is to land. Inlieu of a unique frequency/wavelength of one signature strobe output 722a relative to the other signature strobe output 722 b, coded pulses 804a-c output from landing strobes 100 a-c can be different from codedpulses 804 d-f from landing strobes 100 d-f. Using different repetitiveand periodic series of coded pulses emanating from landing zone 810 arelative to landing zone 810 b, also allows personnel to visually detectthat difference and land aircraft 706 at the appropriate landing zone.

FIG. 8 illustrates two landing zones 810 a and 810 b and three landingstrobes 100 a-c and 100 d-f for each zone in the example drawing.However, it is understood that a landing zone can have one landingstrobe 100, or more than three landing strobes 100. Moreover, there maybe one landing zone 810 with a corresponding one or more landing strobes100, or more than two landing zones 810 having a corresponding single ormultiple landing strobes 100. Landing zone designation system 800 isapplicable to all such configurations in order to determine or designatean appropriate landing for aircraft 706.

FIG. 9 shows a schematic diagram of a system 900 for determiningdistance to landing (DTL) at a decent distance (DD) depending on pixelseparation between a pair of strobes 100 near a landing zone 810 inaccordance with various examples. System 900 relies on personnel placingat least two strobes 100 b and 100 c a predetermined or known strobedistance (KSD) apart. Strobes 100 b and 100 c can be slave strobes (SSs)or, alternatively, the strobes can be a master strobe (MS) spaced a KSDfrom a slave strobe (SS). In the example shown in FIG. 9, KSD is betweentwo SSs 100 b and 100 c. A predetermined distance measured on the groundbetween strobes is stored and thereafter conveyed to the detector 710(FIGS. 7 and 8) in terms of the number of pixels at a landing distance(LD) to be displayed in a landing distance frame appearing on thedetector 710 if the detector 710 were at LD relative to LZ 810.Therefore, N number of pixels would appear within the LD frame ofdetector 710 if aircraft 706 were at LD relative to LZ 810.

System 900 determines the DTL when aircraft 706 is at DD above LZ 810.During descent at remote LZs, visual reference to the landing terraincan be heavily degraded by the turbulent air during approach andlanding. Landing strobes 100 can be arranged in a known geometricpattern, such as a triangle. The landing strobes 100 can be synchronizedwith each other and, more specifically, SS can be synchronized to an MS.The synchronization can be an optical synchronization where MS shown asreference number 100 a can emit a master strobe optical signal 910 towhich the SSs 100 b and 100 c receive and produce corresponding opticalsignals output therefrom which are synchronized to the MS optical signal910. Thus, MS 100 a not only sends its optical signal to detector 710,but also to SSs 100 b and 100 c. The radiation pattern can be adjustedto direct the synchronizing optical signal from MS 100 a to SSs 100 band 100 c. There may be more than two SSs provided there is at least oneSS that can synchronize to an MS.

System 900 allows detector 710 to continuously detect a number of pixelswithin a frame of detector 710 as aircraft 706 descends from distance912 to distance 914, and further. At distance 914, or DD, a Y number ofpixels within a Y^(TH) frame at DD between landing strobes 100 b and 100c are registered. The Y number of pixels detected in the Y^(TH) frame atDD within detector 710 can be compared to the stored N number of pixelsif aircrafts 706 were on the ground at LZ 810. A DTL can then becomputed based on the difference between the Y number of pixels betweenthe optical signals read on the Y^(TH) frame of detector 710 at DD andthe stored N number of pixels. A processor coupled to memory can computethat difference, and the memory coupled to detector 710 can store the Nnumber of pixels. The processor processes the difference, and detector710 provides guidance to, for example, personnel within aircraft 706 inorder to land aircraft 706 at LZ 810, and further informs personnelbased on pixel distances between landing strobes 100 in video frames toindicate the DTL. Knowing DTL assists the personnel, or pilot, toimprove controlled landing in degraded visual conditions.

FIG. 10 shows a top plan view of landing strobes (e.g., landing strobes100 a-100 c). The landing strobes 100 can be placed in a geometricpattern, such as a triangle, around, in, or adjacent to, a landing zone.For example, at distance 912 (FIG. 9), when the first frame of theseries of video frames are taken (FRAME 0), the optical signals emittedfrom landing strobes 100 a-100 c can appear fairly small with a numberof pixels between optical signals shown as X number of pixels withinframe 0 being fairly small. However, as aircraft 706 descends to, forexample, DD (FIG. 9), the optical signals detected within frame DD whenaircraft 706 is at distance 914 (FIG. 9), the optical signal outputoccupies more pixels for each landing strobe registered on frame DD, andthe number of pixels separating the optical signals appearing on theY^(TH) frame (Y number of pixels) is much greater than the X number ofpixels. The processor coupled to detector 710 can compute the DTL byextrapolating Y number of pixels to N number of pixels stored in memorycoupled to the processor. Based on the amount of extrapolation needed toeliminate the difference, the DTL when aircraft 706 is at distance 914,or DD, can be computed.

FIG. 11 shows a block diagram of a system 1100 for detecting opticalsignals from one or more landing strobes 100 in one or more landingzones 810 in accordance with various examples. System 1100 can beincorporated within an aircraft 706 that includes a detector 710.Detector 710 can be configured for detecting the optical signal 720 andthe signature strobe output 722 from one or more landing strobes.Detector 710 includes a camera 1102 having a lens 1104 for receiving theoptical signal 720 and the signature strobe output 722. Camera 1102 maybe coupled to a filter 1106 that communicates with lens 1104 to operateas an optical filter to select, for example, a frequency/wavelength, orfrequency/wavelength range of an optical signal sent from a landingstrobe 100. The filter 1106 therefore tunes the camera system lens sothat a desired signature strobe output can be detected possibly withinone landing zone 810 and not another landing zone, for example. Filter1106 can also be tuned to allow optical signals from multiple landingzones in one geographic area versus that of another, or to discernfriendly landing zones from unfriendly landing zones. Filter 1106 can betuned to a wavelength or frequency, or any other optical signal outputsuch as, for example, intensity or chromaticity.

Coupled to detector 710 can be a processor 1110. Processor 110 is anyform of computing device, such as a microprocessor configured on asemiconductor substrate coupled to any form of storage device, or memory1112. Processor 1110 of system 1100 is coupled to compute placement ofaircraft 706 relative to landing strobes 100, or landing zones 810.Processor 1110 can also be configured to decode a repetitive andperiodic series of coded pulses applied to the optical signals outputfrom the landing strobe 100. Memory 1112 can be used to store anexpected repetitive and periodic series of coded pulses, and processor1110 can read the expected series of coded pulses and compare thoseexpected series of coded pulses to coded pulses applied to the landingstrobe 100 optical signals. If the coded pulses from landing strobes ofone landing zone match the expected coded pulses, then processor 1110will notify, for example, personnel within aircraft 706 which landingzone produced the matched coded pulse output to determine the properlanding zone in which to land the aircraft 706. The output (OUTPUT) fromprocessor 1110 can be sent to a signaling device, such as a display tosignify the appropriate landing strobe 100 or landing zone 810 havingthe matched coded output. Alternatively, memory 1112 can store anexpected frequency or wavelength, and processor 1110 can compare thestored, expected frequency/wavelength to the frequency/wavelengthapplied to the optical signal or signals from landing strobe 100 orlanding zone 810 to send OUTPUT for determining the appropriate landingstrobe 100 or landing zone 810 that produced the matchedfrequency/wavelength.

FIG. 12 shows a flow diagram 1200 of a method for designating landing ofan aircraft 706 and a landing zone 810. Method 1200 begins by storing anexpected signature strobe output 1202 within memory 1112 (FIG. 11) ofthe aircraft. The signature strobe output is then emitted from a landingstrobe unique to the landing strobe or set of landing strobes in alanding zone 1204. The landing strobe can be either placed before thesignature strobe is emitted 1206 or after, 1208. A determination is thenmade whether all landing strobes are placed in the corresponding landingzone 1210, such as the first landing zone or LZ1. If all of the landingstrobes are not placed in, for example, the first landing zone, thenplacement of additional landing strobes occurs. If all landing strobesare placed in corresponding landing zones 1210 and 1212, then thesignature strobe output is received 1214 on detector 710 (FIG. 11). Adetermination is then made on whether the signature strobe output fromthe landing strobe or strobes matches the expected signature strobestored in memory 1216. If there is no match, then a signal is not sentto land the aircraft. However, if there is a match, then not only is asignal sent to land the aircraft, but a signal is output to indicatewhich landing zone the aircraft is to land 1218.

FIG. 13 shows a flow diagram of a method 1300 for deploying one or morelanding strobes 100, or one or more landing zones 810 in accordance withvarious examples. The reflector or other optic elements in the housingof the landing strobe as shown in FIG. 7 can be adjusted or selectedduring assembly 1302 to modify the radiation output from the opticalemitter from the landing strobe. The landing strobe can be dropped froman aircraft 1304, or placed at or near a landing zone. The opticalillumination device can be activated either prior to being dropped,after being dropped, or after being placed at or near a landing zone1306. Moreover, the frequency/wavelength pulse code, or radiationpattern, of the landing strobe or strobes as well as the detector withinthe overhead aircraft can be set either prior to dropping the strobe orafter the strobe is placed, as shown by block 1308.

Upon impact or placement 1310, the actuator and/or biasing mechanism isactivated 1312 to maintain the vanes at a downward angle in contact withthe upper surface of a landing zone. Once all landing strobes have beenplaced 1314, then the placement method is terminated 1316. Otherwise,the process flow is repeated.

FIG. 14 shows a flow diagram of a method 1400 for determining pixeldistance between landing strobes displayed in a camera frame of adetector at a descent distance (DD) above a landing zone for computingdistance to landing (DTL) at the descent distance DD in accordance withvarious examples. The method 1400 begins by setting the landing strobesat a predetermined, or a known strobe distance apart (KSD) at block1402. If the aircraft were at the landing zone, then the optical outputfrom the landing strobes will be displayed in the LD frame at N pixelsapart corresponding to KSD 1404. The frequency/wavelength/pulsecode/pattern of the optical output signals from the strobes are set1406. Moreover, the frequency/wavelength/pulse code/pattern can also beset, or tuned, within the detector to selectively detect thefrequency/wavelength/pulse code coming from the landing strobes, as wellas to remotely set the radiation pattern emanating from the landingstrobes. If the slave strobes are to be synchronized to a master strobe,then the master strobe will emit an optical signal to which the slavestrobe can synchronize 1408. The slave strobe will then emit at regularand periodic intervals an optical signal synchronized to the opticalsignal output from the master strobe.

When determining the DTL, the aircraft upon descent 1404 and at DD, viathe processor, will compute Y pixel number on the Y^(TH) frame 1412. Thenumber of pixels from the Y pixel number to the N pixel number on theN^(TH) frame can then be extrapolated 1414 to compute the DTL 1416.

Determination of distance to landing (DTL) can be adaptive. Due to rapiddeployment or dropping of the strobes 100 at a distance above thelanding zone, the distance between strobes cannot be accuratelypredetermined. Accordingly, the N number of pixels separating strobes100 on the ground need not be computed from the predetermined distanceon the ground. In these circumstances, software in the camera 1102 ofthe detector 710 expects the distance between strobes 100 to expand, orincrease, in the camera frame as the DTL is reduced. The expansion insuccessive frames captured by camera 1102 increases as a tangentfunction approaching 90 degrees as the aircraft gets closer to thelanding zone. The camera software can approximate the approachregardless of the rate of descent and DTL using the amount of expansion,even when the strobes are not precisely pre-placed and known to thedetection system. Adaptive determination is beneficial when the landingstrobes 100 are dropped from the air during scouting prior to landing.

FIG. 15 is a graph of an amount of pixel change as an aircraft 706 isdescending, relative to a height above the landing zone 810. As shown inthe graph, when the distance to landing (DTL) is less than 30 feet, forexample, the rate of pixel change in number of pixels shown betweenlanding strobes increases as a tangent approaching 90 degrees. Whendescending at a constant rate of, for example, 1 ft/sec, the slope ofthe rate of change of the pixel distance between landing strobes is usedto calculate DTL at whatever the descent distance (DD) without requiringpre-determined knowledge of a known strobe distance (KSD) separating thelanding strobes 100.

FIG. 16 is a flow diagram for calculating DTL using the adaptivedetermination methodology. The graph of rate of pixel change relative toheight above the landing zone 80 is stored in memory 1112 shown in FIG.11, and shown in FIG. 16 at block 1602. The rate of pixel changeexpressed as a number of pixels increases per second as the aircraftbegins its approach 1604. Throughout the approach and as the aircraftdescends, the rate of pixel change will increase as shown in the graphof FIG. 15, and will be computed as shown by block 1606. Knowing thechanging rate of pixel change, the aircraft can continue descending to adescent distance (DD) above the landing zone 810 as shown by block 1608.For every change in rate of pixel change, a height above the landingzone 810 can be ascertained by the stored graph of FIG. 15. As noted inblock 1610, the DTL can be determined at the height above the landingzone 810 corresponding to the monitored and previously stored rate ofpixel change corresponding to the particular height, or DTL.

In the foregoing discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . .” Also, theterm “couple” or “couples” is intended to mean either an indirect ordirect connection. Thus, if a first device couples to a second device,that connection may be through a direct connection or through anindirect connection via other devices and connections. Similarly, adevice that is coupled between a first component or location and asecond component or location may be through a direct connection orthrough an indirect connection via other devices and connections. Anelement or feature that is “configured to” perform a task or functionmay be configured (e.g., programmed or structurally designed) at a timeof manufacturing by a manufacturer to perform the function and/or may beconfigurable (or re-configurable) by a user after manufacturing toperform the function and/or other additional or alternative functions.The configuring may be through firmware and/or software programming ofthe device, through a construction and/or layout of hardware componentsand interconnections of the device, or a combination thereof. Unlessotherwise stated, “about,” “approximately,” or “substantially” precedinga value means +/−10 percent of the stated value. The above discussion ismeant to be illustrative of the principles and various embodiments ofthe present disclosure. Numerous variations and modifications willbecome apparent to those skilled in the art once the above disclosure isfully appreciated. It is intended that the following claims beinterpreted to embrace all such variations and modifications.

What is claimed is:
 1. A landing zone designation system, comprising: amaster landing strobe configured to emit a master optical signal atperiodic intervals; a slave landing strobe spaced a predetermineddistance from the master landing strobe and configured to receive themaster optical signal and to generate, from the master optical signal, aslave optical signal synchronized to the periodic intervals; a detectorprovided on an aircraft for detecting the master and slave opticalsignals; and a processor coupled to the detector to compute placement ofthe aircraft relative to the master and slave landing strobes.
 2. Thelanding zone designation system of claim 1, wherein the detectorcomprises a camera coupled to a lens and having a shutter speedconfigured to capture each of the periodic intervals of the emittedmaster and slave optical signals within corresponding frames.
 3. Thelanding zone designation system of claim 2, wherein the detector furthercomprises a filter coupled between the camera and the lens, wherein thefilter is configured to be modified to detect a particular frequency orwavelength range of the master and slave optical signals.
 4. The landingzone designation system of claim 3, wherein the frequency or wavelengthrange is in the visible spectrum.
 5. The landing zone designation systemof claim 3, wherein the frequency or wavelength range is in theinvisible spectrum.
 6. The landing zone designation system of claim 1,wherein the processor is configured to decode a repetitive and periodicseries of coded pulses applied to the master and slave optical signals.7. The landing zone designation system of claim 1, wherein the processoris configured to compare an expected repetitive and periodic series ofcoded pulses stored in memory to a repetitive and periodic series ofcoded pulses applied to the master and slave optical signals todetermine a proper landing zone in which the aircraft is to land.
 8. Thelanding zone designation system of claim 1, wherein the processor isconfigured to determine a proper landing zone in which the aircraft isto land based on the master and slave optical signals being unique toeach landing zone.
 9. The landing zone designation system of claim 1,further comprising a memory coupled to the processor for storing Nnumber of pixels within a landing distance frame corresponding to thepredetermined distance.
 10. The landing zone designation system of claim9, wherein the processor is configured to compute a distance to landingof the aircraft at an approach distance above the landing zone as afunction of the difference between Y number of pixels between the masterand slave optical signals, captured by the detector in the Yth frame atthe descent distance, and the stored N number of pixels.
 11. A methodfor designating a landing zone for an aircraft, comprising: emitting afirst optical signal synchronized to a first master landing strobe at afirst landing zone; emitting a second optical signal synchronized to asecond master landing strobe at a second landing zone; receiving thefirst optical signal and the second optical signal by the aircraft;determining whether the aircraft is to land at the first landing zone orthe second landing zone depending on a difference between the firstoptical signal and the second optical signal; and computing a distanceto landing within the determined first landing zone or the secondlanding zone.
 12. The method of claim 11, wherein said computingcomprises: storing N number of pixels between a pair of first strobes atthe first landing zone appearing on an Nth frame, wherein the distancebetween the pair of first strobes is a known predetermined distance; andcounting Y number of pixels between the pair of first strobes at thefirst landing zone appearing on a Yth frame captured at the distance tolanding of the aircraft above the first landing zone.
 13. The method ofclaim 12, wherein said computing comprises extrapolating a differencefrom Y number of pixels to N number of pixels and corresponding thatdifference to the distance to landing within the first landing zone. 14.The method of claim 11, wherein said computing comprises: storing Nnumber of pixels between a pair of second strobes at the second landingzone appearing on an Nth frame, wherein the distance between the pair ofsecond strobes is a known predetermined distance; and counting Y numberof pixels between the pair of second strobes at the second landing zoneappearing on a Yth frame captured at the distance to landing of theaircraft above the second landing zone.
 15. The method of claim 14,wherein said computing comprises extrapolating a difference from Ynumber of pixel to N number of pixels and corresponding that differenceto the distance to landing within the second landing zone.